John G. Frelinger, Ph.D.

My laboratory has a number of interests united by the common theme of T cell recognition. One focus of research has been the generation and maintenance of effective T cell responses to tumors. It has become apparent that anti-tumor responses can be directed against differentiation antigens. Thus, even with multiple mechanisms of establishing and maintaining tolerance, tolerance is not absolute. We hypothesize that it is possible to direct an effective response against tumors by inducing an autoimmune response to organ-specific antigens. To examine this hypothesis, we will use transgenic mice lines we have developed which specifically express human PSA in the prostate and investigate how this expression affects their ability to generate CTL responses to human PSA using novel immunization strategies. In this light, we have been working on developing novel viral vectors for immunization. Helper free herpes amplicons, plasmid based vectors that have an extremely large coding capacity, are attractive viral vaccine candidates for expressing recombinant proteins in vivo for immunization. The amplicon system has particular promise since it encodes no viral gene products and we have shown it very effectively infects dendritic cells. In collaboration with Edith Lord and in conjunction with Tom Foster's laboratory in the Department of Imaging Sciences, we have devised imaging approaches to look at the early steps in immunization and at the effector T cells generated. These studies will contribute to the rational design of immunotherapy for tumors as well as for HIV. We also believe that many of the techniques and approaches will be applicable to other infectious agents as well. In this regard, we are collaborating with investigators at University of North Carolina to identify T cell epitopes of Francisella tularensis. Francisella tularensis (FT) is a gram negative bacterium that is able to infect a wide range of mammalian hosts. FT has several properties that suggest could be developed as a biological weapon, including its ability to be aerosolized and its low LD50. Indeed, it has been asserted that FT was used as a bioweapon in World War II. Unfortunately relatively little information is available concerning the detailed cellular mechanism of resistance to re-infection either in humans or in experimental animals. However, as expected for a pathogen that grows largely intracellularly, T cells are believed to be a critical component in resistance to reinfection and recovery from primary infection. My laboratory has developed a technique called the TCAD ( the T-Cell antigen discovery technique) to identify and improve T cell epitopes, originally in the context of tumor vaccines. We have recently modified this system to large-scale screens for the identification of T cell epitopes from FT using this system which takes advantage of the tremendously enhanced efficiency particulate antigen cross-priming and a novel reporter system of T cell activation. It is hoped that the identification of the T cell epitopes recognized will yield to a batter understanding of the nature of a protective response and ultimately a defined vaccine.